Pain is defined as an unpleasant sensory or emotional experience associated with actual or potential tissue damage. It is epidemic in our country. It is the single most common complaint seen in healthcare. Pain-related prescriptions account for more than one of seven medical prescriptions written each year. The national medical costs alone exceed 100 billion dollars annually. The overall costs are several times greater when social costs of lost productivity, disability indemnity, legal settlements, fraud and other issues are factored into the complex physiologic and/or psychological pain experience. Of the categories of pain, musculoskeletal and neuropathic pains are among the most vexing. These pains often result from alleged injuries where the psychosocial milieu is most intricate. In these settings, questions of etiology, prognosis, treatment, impairment, disability, depression, anxiety, liability, and fraud often coexist. These issues are compounded because the pain complaint is largely subjective and is difficult to assess in an un-biased, qualitative and quantitative fashion.
This problem is made worse when pain becomes chronic. In most circumstances, acute pain is self-limited and will resolve. For example, 80% of all Americans experience low back pain at least once during their lifetime. For the majority, these pain attacks will improve within four weeks to the point that individuals return to their activities (such as work). Twenty-five percent of all lower back injuries persist for more than one month; this minority account for 75% of all healthcare and other expenses related to low back injuries. Each year, 3-4% of the population will be disabled temporarily (largely due to musculoskeletal injury) and 1% of the working-age population is permanently and totally disabled.
The problem is of great national concern. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has suggested that pain is the fifth vital sign and should be monitored as vigilantly as blood pressure, pulse, temperature and respiratory rate. Pain, however, is often inadequately evaluated and managed by healthcare professionals because of the complex intermix of components that underlie the individual patient's pain experience. Unlike the other “vital signs [that are quantifiable and unitary],” pain complaints have been difficult to analyze in a pragmatic and cost-effective fashion. Better methodologies are needed to address this national epidemic.
A brief review of the more complete definition of pain offers a starting point to the complex issues involved. According to the International Association of Pain (IASP), pain can be defined as “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” The subsequent notations add the following clarifications and distinctions:
“Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. Biologists recognize that those stimuli which cause pain are liable to damage tissue. Accordingly, pain is that experience we associate with actual or potential tissue damage. It is unquestionably a sensation in a part or parts of the body, but it is also always unpleasant and therefore also an emotional experience. Experiences which resemble pain but are not unpleasant, e.g., pricking, should not be called pain. Unpleasant abnormal experiences (dysesthesias) may also be pain but are not necessarily so because, subjectively, they may not have the usual sensory qualities of pain.
Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause.”
This definition introduces the problems underlying the proper assessment of the pain experience. A paraphrase of the above yields the following conceptual framework. An individual's pain complaint is always an emotional, psychological experience related to an unpleasant sensation in parts or parts of the body that may occur in the presence or absence of any pathophysiologic (i.e., bioanatomic) cause. One must then factor into the consideration, the known dilemmas of addiction, secondary gain, factitious disorders and malingering. The net result is that an individual's pain complaints can be a complex mixture of pathophysiologic causes, emotional factors, and social components. Each of these domains merits some further discussion.
The pathophysiologic component of the pain experience is the usual focus of the healthcare professional. Using musculoskeletal and peripheral neuropathic pain as the model, the standard medical paradigm seeks to identify the sensitive (i.e., “painful”) body region or part and relieve the tissue sensitivity. This is usually attempted using one of several approaches: (a) medications, such as muscle relaxants, anti-inflammatory medications, analgesics, neuropathic pain medications, and others; (b) physical modalities (e.g., physical therapy, chiropractic care, massage, acupuncture, or TENS unit devices); (c) peripheral nerve injections (e.g., anesthesiologic techniques such as nerve blocks, sympathetic ganglia blocks, epidural injections); and (d) surgical techniques (e.g., orthopedic or neurosurgical techniques such as joint surgery, spinal surgery, etc.).
Each of the aforementioned medical approaches is predicated on the notion that there is pathophysiologic tissue sensitivity as the core element underlying the patient's voiced complaint. If the sensitive tissue is properly identified and treated, then the pain complaint will be largely improved. Even a cursory review of the IASP definition of pain quickly demonstrates that the situation cannot be naively reduced to such a singular perspective. In many pain models, the emotional and social domains of the pain experience have been often largely disregarded or ignored during the traditional medical assessment and management of the patient's complaints. The net result is that there has been a both an under- and over-utilization of medical care because of inaccurate or incomplete diagnoses. Two simple statements should suffice to illustrate the point. If the major substrate for a patient's voiced complaint lies in the domain of emotional or social etiology (e.g., depression, anxiety, anger, secondary gain), then physical therapy, epidural steroid injections and low back pain will not effectively address the symptoms. Alternatively, if a patient's enduring pain is labeled as emotional, then the pain can go under-managed.
There are now a large number of population studies that demonstrate that diagnostic physician errors tend to underestimate and overestimate the psychosocial factors that impact patient's pain complaints. For example, 27% of all patients suffering from chronic arthritis suffer from major depression; many of these individuals go under treated for their depression. Similar figures exist for many other chronic musculoskeletal conditions. On the other hand, other studies find that the majority of patient's with chronic non-malignant pain do not receive adequate pain control from their treating physicians. Methodologies that properly identify and separate the pathophysiologic, emotional and social components of an individual's pain symptoms will help identify the appropriate approach to the subject's treatment. There will be more accurate diagnoses and better utilization of healthcare resources (with a reduction or cost and an improvement in outcome).
The co-morbidity of pain and emotional conditions has been established in almost every population study where it has been sought. For example, 27% of patients with arthritis suffer from identifiable depressive disorders and 35% had identifiable anxiety disorders. There has been a clear link established between fibromyalgia and psychiatric disorders. Similar juxtapositions have been found in failed low back syndrome, neuropathic pain syndromes such as diabetic neuropathy, and others.
One relevant question is that of etiology: whether the emotional disorder is caused by or causative of the pain complaint. Population studies suggest that both situations can arise. There are certainly cases where the family and personal history of depressive and anxiety syndromes pre-existed the development of pain complaints. Alternatively, there are certainly circumstances where there has been no antecedent psychological history prior to an identifiable pain syndrome and the subsequent development of a psychiatric disorder. There are three major divisions of emotional disorders that will be separated here for nosologic and analytic purposes.
These include psychotic disorders, depressive disorders, and anxiety disorders. They are not mutually exclusive and may co-exist. Frank psychosis can co-exist with pain syndromes. Fortunately, this is a relatively rare combination and will not be discussed further. As mentioned above, anxiety disorders and pain syndromes can be co-morbid. The anxiety syndrome may be generalized and have no causative relationship to the specific pain syndrome, (e.g., a patient with a generalized anxiety disorder may get into a car accident and then suffer symptom magnification as a manifestation of the underlying psychiatric syndrome). The anxiety syndrome might be based on pre-existing phobias and fears that are situationally specific (e.g., a patient with prior shoulder problems might become excessively anxious about a new knee injury). In both these cases, the anxiety syndrome has a primary causative relationship to the experienced pain symptom. Alternatively, an individual with a painful back injury may become anxious because his job security is threatened; this would be an example of a generalized anxiety secondary to the pain syndrome. Similar examples can be evoked regarding the co-existence of a depressive disorder and a pain syndrome. It also should be noted that anxiety/depression disorders can occur together. Some patients will have both.
The above brief outline demonstrates that the clinician faces a difficult conundrum when confronted with a chronic pain patient (where these interactive problems may or may not be manifest). Methodologies that rationally and clearly identify those individuals with significant emotional components to their pain complex would again improve diagnostic accuracy and management. As previously mentioned, 25% of all individuals with low back injuries fail to return to work within one month of injury. These individuals account for 75% of all costs associated with the management of low back problems. Large population studies document that there is a poor correlation between the severity of the injury, the pain complaints, radiological findings, and the outcome. Experience suggests that up to one-half of all these “treatment failures” may be due to improperly diagnosed and managed emotional factors.
Two of the social ills that taint the discipline of pain management are substance abuse and malingering. Substance abuse can be subdivided into two categories: social abuse and addiction. Addiction has a specific diagnosis as “a primary, chronic neurobiological disease, with genetic, psychosocial and environmental factors influencing its development and manifestations.” It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving.” Drug abuse, on the other hand, is characterized by “the conscious, often psychosocially motivated use of illicit substances and medications outside the scope of usual medical practice, but with the ability to stop drug use when harmed.”
Allied with these are the issues of drug diversion for sale and distribution. This problem is again epidemic in our nation. In 2002, estimates suggested that 30 million Americans used prescription pain medications for non-medical purposes. In the same year, 1.5 million Americans (i.e., 0.5% of the population) abused or depended on prescription pain medications for non-medical reasons. Extrapolating from this data, one can estimate that there is a substantial risk that substance abusers or addicts or others will present routinely to physicians complaining of chronic pain. This problem will be even more complex when such individuals have identifiable anatomic entities that are often correlated with but are not inevitably associated with pain syndromes (e.g., herniated spinal discs, arthritic bony changes, fibromyalgia). Some studies suggest that up to 10% of all patients with chronic pain syndromes demonstrate aberrant behaviors reflective of possible drug abuse. Some of this may be due to unmanaged pain, emotional domain issues or social issues. A key challenge for the future will be the accurate assessment of this population of individuals.
Another social ill of our society is malingering for secondary gain. Malingering is the feigning of disability or symptoms in the effort to avoid one's duty or to obtain secondary compensation. It covers a wide spectrum of misbehavior from complete fabrication (i.e., faking an injury) to partial symptom magnification of a known and reproducible injury. It must be distinguished from the emotional disorders discussed above (these can also be feigned) and true psychiatric disorders (i.e., factitious disorders commonly known as Munchausen's syndrome or Munchausen's by proxy). The prevalence of malingering in our society is unknown. It is higher in cases of pending litigation and indemnity. Significant malingering elements may be present in approximately 5% of all workers' compensation cases. Patient fraud is rampant in Social Security, Medicare and Medicaid. There is an estimated $1.6 billion dollars of Medicaid fraud perpetrated in Florida each year. Again, methodologies that objectively identify the existence of socially mediated pain complaints will reduce healthcare and indemnity costs in our nation.
A final correlate of the emotional and social domains of pain management is the domain of motivation. It is related but not completely dependent of the other aspects of pain complaints. Individuals can suffer pathophysiologic pain complaints and/or emotive pain complaints; these patients however may or may not be motivated to improve. For example, a patient with a chronic low back pain and no emotional overlay may still not be motivated to rehabilitate. Conversely, a patient with a severe generalized anxiety disorder may truly wish to improve through medications and counseling. As an aside, socially-mediated pain complaints do not require motivation for improvement of their pain symptoms, because by definition the pain symptoms are largely feigned; the key then is identification. The old adage states “where there is a will, there is a way.” Conversely, one might state “where there is no will, there is no way.” Once the major domains underlying a subject's pain symptoms can be identified, then secondary testing can elucidate whether or not there are issues with motivation.
Although population studies have clearly identified the scope of the problem in the assessment of chronic pain, applying these findings to the individual patient has not been successful. The complexities of the problem and the limitations of the “bedside” evaluation have resulted in significant diagnostic uncertainty and error.
The current medical paradigm for the assessment of an individual presenting with pain symptomotology is quite imprecise. After a clinical history, the physician attempts to verify the pathophysiologic pain by a clinical examination. The physician examines the patient by using an acceptable “painful stimulus” while monitoring mostly the patient's verbal response and associated body reactions. The stimulus is usually an unmeasured physical input such as palpatory pressure, active or passive range of motion, or a sensory stimulus (such as rubbing or a pin prick). The patient's monitored response is usually verbal (e.g., “That hurts”) but may be associated with other physical manifestations such as wincing, withdrawal, or others. There are several limitations to this paradigm; these will be treated separately.
One limitation is the ambiguity of the patient response. The physician is currently largely dependent on the patient's response to the ungraded stimulus. In cases of substance abuse, addiction, medication diversion, social secondary gain, malingering, and factitious disorder, the patient can feign or exaggerate the response to mislead the physician into an improper assessment as to diagnosis or severity of the condition. This will lead to over-prescribing of medications, diagnostic tests or other treatment. It can lead to unfair compensation or assignment of social disability.
Further, in patients with emotional disorders, the pain symptoms may be tainted by an unconscious exaggeration of the stimulus and or its consequences. Patients with anxiety will tend to exaggerate the pathophysiologic intensity of the problem (e.g., the person who is afraid of the dentist will jump when the dentist touches the teeth; this does not mean that the tooth itself is biologically tenderer. A depressed patient may see the world in more plaintive and melancholic overtones so that everything “hurts more.” This then can lead to inaccurate assessment of the underlying biologic component of the pain. Conversely, the patient with under treated pain may have a secondary anxious and depressive presentation that leads the doctor to conclude that the problem is primarily psychological.
Another limitation is the incomplete assessment of the patient response. As delineated in the definition of pain, the pain response has other components to its biological profile. These include the autonomic and physiologic responses that go largely unmonitored by the bedside physician. They include changes in vascular responsiveness (e.g., pulse rate, blood pressure, and peripheral vascular tone), skin resistance (due to sweating and other responses as measured by Galvanic changes), and overall muscle tone (e.g., anticipatory and reactive muscle tensing). These responses are extremely reproducible and follow very well known biologic principles and mechanisms. By routinely assessing the complex pain patient with these additional measures, the physician will be better able to grade the pain response and its components. This will be discussed more completely below. These well known observations will allow an expanded and more precise delineation of the individual's voiced pain experience.
Further, the physician must rely on his observational experience and acumen to assess all factors concerning the pain response. These include the severity of the response, the presence or absence of anticipatory (i.e., anxiety-related) phenomena, the presence or absence of post-stimulus emotive responses, and patient forthrightness. By monitoring and recording the autonomic and physiologic parameters just introduced, the physician will be better able to assess the three major domains of the patient pain profile.
Another limitation is the imprecision of the evocative stimulus. The clinician generally uses non-measured stimuli to create his observations. They are usually applied once and therefore do not guarantee reproducibility and accuracy. If the physician palpates the sore knee once, the patient complains and the physician infers. This leads to a great deal of imprecision in the inferences drawn. If a measured stimulus is applied repetitively in a systematic fashion and then combined with precise and comprehensive monitoring, then improved diagnostic accuracy will result.
The diagnostic uncertainty and error concerning the individual with pain complaints results in the current quagmire that confronts the medical community and society in general when dealing with this epidemic problem. The current quagmire that confronts the medical community and society in general when dealing with this epidemic problem.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for a more efficient way of evaluating pain in humans.